When you purchase something on Amazon or with iTunes you have to use your real name, credit card information and address. Amazon and Apple/iTunes has all of that information. Apple by the way has the largest online store.

The difference is you provide both services with your email address, password and your profile url / name is less relevant. Well, Google already has your email ( gmail ) address, now google wants your real name ( identity) to go with your gmail address. This could be very helpful to google AND you in the future in terms of matching transaction, matching search results to your content and connecting your identity across the web with your other social networking content/profiles. Also it could help reduce spam and people leaving / making anonymous comments where they feel as though they can hide behind a computer screen and say whatever without any consequences.

At the end, I think everyone will see the value of google+ in terms of real name and identity. Yes it could overlay with other services and probably will when the google+ api is released. You may be able to use google+ for your blog comments or openID login or as a publishing platform all together.

In the mean time, join the other real name / people on google+ or continue to use your other favorite other social network and stop complaining or launch your own.